Perception of risk is a central component of many theoretical models of sexual decision-making and public health efforts designed to reduce STD risk behaviors among adolescents often aim to increase perceived risk for STDs (PRSTD). Empirical trials have often failed to link adolescents' perceptions of risk for STDs to subsequent STD risk behaviors but methodological weaknesses make it difficult to interpret the null results. More rigorous research is needed to evaluate the role of PRSTD. The proposed longitudinal research will (1) develop an elaborated measure of PRSTD; (2) determine its ability to predict STD risk behavioral intention, subsequent STD risk behaviors and STDs; and (3) examine whether PRSTD plays an independent role from the constructs found in the Theory of Planned Behavior. Our main focus is on high-risk sexually experienced adolescents (14-18 years old) with STDs. In Phase 1 of the proposed project, we will determine adolescents' perceptions of the severity of various STD-related health outcomes. In Phase 2, we will develop and evaluate the psychometric properties of an elaborated PRSTD scale which spans different levels of severity, utilizes different ways of expressing risk, taps both absolute and relative risk and is specific to partner type. In Phase 3, we will test the ability of the new PRSTD scale to predict partner-specific STD risk behavioral intention, subsequent STD risk behaviors and STDs among 500 sexually experienced adolescents with a current STD. We will reinterview and collect specimens for gonorrhea, chlamydia, syphilis and herpes (if they had no herpes antibody at baseline) from subjects at six months. However, subjects diagnosed with a new reportable STD during the six months will be reinterviewed around the time of the diagnosis. In addition, we will determine whether PRSTD predicts STD risk behaviors among sexually experienced adolescents without a current STD and predicts timing of sexual debut among sexually inexperienced adolescents.